The present invention is directed to a starch-oil type sizing composition and glass fibers that have been treated with the composition. The term "starch-oil sizing " is a term commonly used in the art and means a treatment for fibers having at least one starch along with oil, wax or other nonionic lubricants and mixtures thereof, which is applied to the glass fibers to impart certain properties as discussed below.
Glass fibers are produced by flowing molten glass via gravity through a multitude of small openings in a precious metal device called a bushing. Typical glass fibers are described in The Manufacturing Technology of Continuous Glass Fibres, by K. L. Loewenstein, Elsevier Scientific Publishing, 1973, at page 29, Library of Congress Catalog Card No. 72-97429. Among the commonly used glass fibers are, for example, those known as "E glass", "S glass", "D glass" and are typically between 3 and 30 microns in diameter.
In close proximity to their formation, these fibers are treated with a sizing composition which serves to protect the fibers from abrasion arising from contact with each other or with processing machinery. The aqueous sizing composition is applied by sprayers, rollers, belts or the like. The sized glass fibers are gathered into bundles or strands comprising a plurality of individual fibers, generally from 200 to more than 3000. The sized glass fibers generally have between about 0.05 and 5 percent of sizing composition based on the weight of the glass fiber.
After their formation and treatment, the strands are wound into a spool or "forming package". The forming packages are usually dried in either an oven or at room temperature to remove the moisture from the fibers. For certain uses, the fibers are then typically wound onto a bobbin via conventional textile twisting techniques such as a twist frame.
One function of a sizing composition is to improve the performance of the fibers during further processing. Such further processing can include textile applications such as weaving of the fibers, which involves removing the fiber from the bobbin and guiding the fiber over or through a series of guide bars and other points of physical contact where wear could occur. Manifestation of such wear can be seen in the buildup of broken filaments or "fuzz" on the contact points, an increase in static electricity, poor quality of the woven product, as well as the shedding of the sizing from the fibers, or the breaking of the strand itself during weaving. Another function of a sizing is to impart to fabrics which are woven from the treated fibers a surface which is smooth and which has few visible defects.
The strands of treated glass fiber may also be used in non-woven applications such as the manufacture of fiber glass reinforced tape. In this application the strand can undergo abrasion and wear similar to that experienced in the woven applications as it is removed from the bobbin and processed.
An example of a starch-oil sizing is disclosed in U.S. Pat. No. 4,681,805 to Puckett. The sizing disclosed has a poly(oxypropylene) polyol as the sole starch film-forming modifier in order to reduce gummy deposits on equipment.
It is an object of this invention to produce strands of glass fiber having a moisture-reduced residue of a starch-oil type sizing composition which results in reduced fuzz production, reduced shedding, greater strand integrity and which produces a smooth woven surface with few visible defects.